This invention relates to an exhaust duct for internal combustion engines and more particularly to a connector for exhaust ducts.
As shown in FIG. 1 of the accompanying drawings, a conventional exhaust duct assembly used in automotive vehicles includes a pair of upstream exhaust ducts 2, 3 connected at one end to an exhaust manifold 1, a Y-shaped connector 4 connecting the other ends of the exhaust ducts and an exhaust duct 5, two mufflers 6, 7, an exhaust duct 8 connecting two mufflers 6, 7 and a tail exhaust duct 9 (see Nissan service weekly No. 475 "Nissan skyline" published October, 1982 by Nissan Motor Company Ltd.).
As shown in more detail in FIG. 2, two upstream branches 4a, 4b of Y-shaped connector 4 snugly receive the ends of exhaust ducts 2, 3 and the downstream end of connector 4 receives one end of exhaust duct 5. In this exhaust duct arrangement, exhaust emissions from upstream ducts 2, 3 can mutually interfere constructively in connector 4, whereby the exhaust pressure waves can not enter downstream exhaust duct 5 easily. This causes part of the exhaust pressure waves to propagate upstream via exhaust ducts 2, 3, which interferes with other in-coming exhaust pressure waves, and causes exhaust impulse waves, thereby producing disturbingly loud noises. Furthermore, the upstream-propagating pressure waves lower exhaust efficiency and engine output.